1. Field of the Invention
The present invention relates to a slide fastener tape composed of warp yarn knitting structure having an element attaching portion on which a fastener element is attached, the element attaching portion being formed by knitting in a swollen state along a side edge portion of a knitted tape main body.
2. Description of the Related Art
In recent years, a slide fastener has been attached to various kinds of flexible clothes, so that a fastener tape itself has been demanded to have flexibility. Therefore, various kinds of knitted fastener tapes having much more flexibility than woven fabric have been developed. Particularly, in view of its flexibility and stability of the state, warp knitted fastener tape has been widely used.
For example, according to Japanese Utility Model Publication No. 56-16088, as a first embodiment thereof, a tape main body is formed of double structures by double row needles and an element attaching portion to be connected to the main body is formed of a double tricot knitting structure by the double row needle in a swollen state, so as to surround a core material. Further, as a second embodiment of the same publication, an edge portion of the tape main body on a side of the element attaching portion is formed of the double structures by double row needles and the element attaching portion to be connected to the main body is formed of the double tricot knitting structure by the double row needle so as to surround the core material.
According to Japanese Patent Application Laid-Open No. 8-56713, for example, the tape main body is formed of single layer structure by only a needle of the front surface or rear surface. The element attaching portion is composed of double chain knitting structure knitted with two knitting yarns disposed on the core material and both sides thereof, a weft yarn inserting structure by weft yarn inserted with being swung symmetrically to the right and left between knitting patterns of the chain knitting structure and another weft yarn inserting structure comprised of the tricot knitting structure, chain knitting structure and normal weft yarn knitting structure, composing part of the tape main body. The double chain knitting structures and the weft insertion yarn of the element attaching portion are respectively knitted into the front surface and rear surface of the tape main body alternately so as to form the element attaching portion in a substantially completely rectangular section.
In the fastener tape for slide fastener composed of such warp knitting structure, irrespective of whether the tape main body is composed of the single structure by a single row needle or the double structures by the double row needles, the aforementioned element attaching portion is formed such that it is swollen with a larger thickness than the tape main body so as to surround the core material extended in the longitudinal direction with the double warp knitting structures.
Therefore, if it is intended to form the swollen element attaching portion integrally with the tape main body by the warp knitting structure, necessarily it has to be knitted by means of a double row needle knitting machine. To form the element attaching portion having the aforementioned structure, the core material is provided in the middle of the double row needles and the element attaching portion is formed by double row needles.
If it is intended to form the tape main body with double structures by double row needles like the element attaching portion, the core material is disposed on the line passing the center of an end face in a side edge portion of the tape main body in the longitudinal direction because the tape can be formed symmetrically to the front and rear surfaces. Therefore, it is possible to form the swelling state on the front and rear surfaces of the element attaching portion symmetrically to the front and rear surfaces.
If the tape main body is intended to be formed of a single structure using only one side of double row needles, however, the core material is deviated toward the-other side of the double row needles from the center of the end face in the side edge portion of the tape main body, even if the side edge portion in the tape main body is formed of double structures as disclosed in the second embodiment of the aforementioned Japanese Utility Model Publication No. 56-16088 as well as in the fastener tape disclosed in the aforementioned Japanese Patent Application Laid-Open No. 8-56713. Consequently, the swelling state of the element attaching portion is also deviated toward the other side, so that upon implanting the element, the element cannot be implanted equally on the same plane, thereby causing some disadvantages such as obstructing a smooth sliding of the slider.
According to the knitting structure disclosed in the publication, the warp knitting structure in the tape main body is composed of the chain knitting structure and weft yarn inserting structure. The weft yarn inserting structure of those structures is only interlaced with needle loops in part of the double tricot knitting structure, which is the warp knitting structure in the element attaching portion, and connected to the element attaching portion. Therefore, knitting pattern density at the connecting portion tends to be coarse, so that it is difficult to secure a desired attaching strength of the element.
If the tape main body is composed of the double structures as described above, the main body is formed thick so as to increase rigidity, so that flexibility expected for knitted fabric may be lost. Therefore, an initial purpose thereof cannot be achieved.